1. Field of the Invention
The present invention relates to a liquid crystal display device and more specifically, to a liquid crystal display device using ultrathin glass.
2. Description of the Background Art
Liquid crystal display devices recently suggested include a liquid crystal display device originally intended for curvature (curved display), and a liquid crystal display device capable of displaying two screens (double screen display) for the presence of a parallax barrier placed on a display surface of a liquid crystal panel.
These liquid crystal display devices both use ultrathin glass. As an example, Japanese Patent Application Laid-Open No. 2003-337550 is intended to realize a liquid crystal panel capable of being bent flexibly and capable of being used also as a curved display. In order to achieve this intention, Japanese Patent Application Laid-Open No. 2003-337550 discloses a liquid crystal panel using a ultrathin glass substrate made of ultrathin glass and having a thickness of from about 0.01 to about 0.15 mm. Likewise, Japanese Patent Application Laid-Open No. 5-249422 (1993) discloses a liquid crystal panel and a method of cutting the liquid crystal panel. This liquid crystal panel is intended to be used as a reflective liquid crystal display device, and uses a ultrathin glass substrate that is also made of ultrathin glass and having a thickness of from 0.1 to 0.2 mm provided as one of a pair of substrates.
As described above, an ultrathin glass substrate of a thickness of about 0.1 mm is being used widely in liquid crystal display devices including a double screen display, a curved display, and a reflective display. In a step of manufacturing such liquid crystal display devices, while two glass substrates holding a liquid crystal layer therebetween are in the form of cell substrates having the size of a mother substrate, the thickness of at least one of these substrates is reduced to make this glass substrate ultrathin glass, and thereafter, the substrates are cut into the sizes of individual liquid crystal panels.
For cutting of the glass substrates to divide the glass substrates into the liquid crystal panels, a scribe line being a cut flaw showing the starting point of cutting is first formed on a glass surface. More specifically, a scribe line is formed with a scribe cutter (or scribe wheel) on a surface of ultrathin glass between seal patterns of adjacent panels.
When the scribe cutter (or scribe wheel) comes into abutting contact with the surface of the ultrathin glass to apply a load thereon, the ultrathin glass is distorted largely. The amount of the distortion varies depending on the change of a distance between a scribe line and a seal pattern. This makes repulsive force unstable, so a scribe line cannot be formed favorably.
Further, fluctuations of a seal position, a seal width, and the accuracy of a scribe line are generated even on the same scribe line to make it impossible to keep a distance between a seal and a scribe line constantly. This involves change of a scribe condition.
As a result, a cutting damage such as a tiny crack may be left in a cutting surface, or a glass substrate may be broken during its cutting. Such a failure reduces yields.
In response to the aforementioned problems, a seal pattern to bond glass substrates as a pair together may be placed directly below a scribe line, or a supporting member used to avoid distortion of glass may be provided directly below or near a scribe line.
In order to place a seal pattern directly below a scribe line, a seal peeling support layer should be formed in advance on a TFT (thin-film transistor) to peel a seal member stably when a fragment at a terminal extraction part is removed, for example. Even in this case, it may still be hard to peel a seal member stably without involving a damage on the TFT substrate.
Meanwhile, forming a supporting member used to avoid distortion of glass and placing the supporting member directly below or near a scribe line by using the same material and the same technique as those of a columnar spacer does not generate a problem to be caused during removal of a fragment at a terminal extraction part. However, the supporting member is formed before a rubbing step. So, if placed on the upstream side of rubbing process near a display region (downstream side of the rubbing process corresponds to a direction in which a rubbing roller travels), the supporting member becomes an obstacle to the rubbing process. This generates defective orientation of liquid crystal to cause failure such as nonuniform display.
A liquid crystal panel may be manufactured by using vacuum injection process. In this case, an inlet region being an opening portion of a main seal is provided for deaeration or degassing of a cell, or for injection of liquid crystal into the cell, leading to the probability of failing to place supporting members of a number that avoids distortion of ultrathin glass completely. In this case, if supporting members are placed densely in a region of a cutting line including an inlet region and except the inlet region thereof without consideration for distortion of the inlet region, the inlet region and the region except the inlet region cannot be given optimum scribing pressures simultaneously. So, increasing or reducing scribing pressure still generates defective cutting in either region.